Police raided six homes in Leeds searching for explosives and computer files that would shed more light on what were believed to be the first suicide bombings in Western Europe. They arrested a man, identified by the British news agency Press Association as a relative of one of the suspected bombers.
A town councilor told The Associated Press that at least three of the presumed suicide bombers were British citizens of Pakistani ancestry.
One bomber was thought to be Shahzad Tanweer, a 22-year-old cricket-loving sports science graduate, and another was a teenager, Press Association reported.
Press Association said the men had driven a rental car to Luton, 30 miles north of London, and then boarded a commuter train to London's King's Cross station.
Police closed Luton's train station and carried out a controlled explosion on a parked car, which the BBC reported had explosives.
Closed-circuit TV video showed all four men arriving at King's Cross by 8:30 a.m. on Thursday, about 20 minutes before the blasts began, Peter Clarke, head of the Metropolitan Police anti-terrorist branch, told a Scotland Yard news conference.
The police searched ______homes in attempt to find attack-related explosives and computer files.

A. three
B. four
C. five
D. six